Nearly every residential and industrial dwelling or facility, an automobile with an internal combustion engine, or a vacuum cleaner incorporates some kind of an air supply or air treatment system. These systems range from a simple ventilation duct to automatic air conditioning installations that may include heating, cooling and humidity control devices. Typically, mass of gas (air, in particular) is driven through the dwelling or machinery by means of a forced convection. This requires use of a pump or air blower. Also, they usually include filtration components (filters). The purpose of the filters is to remove airborne contaminants that may adversely effect health of humans and animals, cause malfunction or reduction in efficiency of equipment, and deposits of soiling compounds onto various surfaces.
In the automotive applications, air filters are used with the internal combustion, engines. A clogged air filter not only decreases the engine efficiency in terms of the output power and fuel consumption, but also increases the engine wear and reduces its lifetime. In this patent, we use word “air”, although it should be understood that any gas or mixture of gases can be monitored in a similar manner.
A typical air filter consists of a supporting frame and a filtering layer or layers, often fabricated of paper or a mesh made of polymer fibers. The entire mass of the treated air passes through the filter. The airborne contaminants (dust, pollen, e.g.) are captured by the filtering layer using either mechanical or electrostatic action. When a significant amount of contaminants is deposited onto the filter (the filter becomes clogged), the filter's resistance to air flow increases. The clogging may have multiple negative effects: 1) the increased air flow resistance will reduce efficiency of the air treatment system, 2) the energy consumption will rise, and 3) the air flow may dislocate captured contaminants and make them airborne again. The air filter should be changed or cleaned whenever the clogging reaches an unacceptably high level. An advisable timing of such maintenance will depend on many factors—quality of supplied air, humidity, temperature, geometry of the dwelling and air ducts, power of the blower, etc. Due to many unpredictable and continuously changing factors, the appropriate timing can not be accurately guessed and, therefore, a more reliable and efficient way of the filter clogging detection is highly desirable.